What could be wrong if there is a large amount of blood found in your feces? i've had constipation problems since i was a toddler and 18 years later i'm still struggling with that problem. but recently i've been finding large amounts of blood in my feces

There : There are multiple possible sources of the blood - polyp, anal fissure, anal fistula, internal hemorrhoid, external hemorrhoid. Recommend that this be medically evaluated.

Depending: On age, most common cause is constipation and hemorrhoids; however always concerned for colon pathology such as inflammation or colitis, colon polyps, colon cancer. You need to see a colon and rectal doctor or a GI doctor for a thorough evaluation and possible colonoscopy. Do not delay.